Device for making exposures on lenticular films



July 4, 1944. A. H. J. DE l. SAINT GENlEs 2,352,864

DEVICE FOR MAKING EXPOSURES ON LENTICULAR FILMS Filed Feb. 10, 1940 oFW? 7 M .6 w w 6 6 5. 5 5 1 A 4 4 nl' c 2 MW 2 ,2 /M A lo E `.mv

Mido/4 swwwram/fi Patented July 4, 1.944

UNITED STATES PATENT F FICE Anne Henri Jacques de Lassus Saint Genies,Versailles, France; vested in the Alien Property Custodian ApplicationFebruary 10, 1940, Serial No. 318,344 In France January 27, 1939 5.Claims.

The present invention relates to combined optical blending anddispersing devices for eifecting exposures on lenticular films as usedfor ex- The lack of coincidence, is much more pronounced the further theobject is removed from the plane of sharp definition. It shows itself,on projection of films, in the production of coloured fringes, and theselatter are the more pronounced the greater the aperture and the greaterthe focal length of the camera lens used for making the exposures.

To overcome this drawback inherent in making exposures in colour onlenticular films, various means have already been proposed utilizingmirrors or prisms, either to give to two of the colour bands of thefilter, or to three of them, the breadth of one of these bands as imagepoint base, or by blending each of the image points partially with theother two.

In the rst case, there is achieved the dispersion of the relativelynarrow beam of light striking the entry lens, and its distribution overthe entire breadth of the filter, but this result is obtained at thecost of a considerable reduction in the light yield of the lens.

In the second case, the beams striking the lens are blended over thebreadth of the filter, but owing to the reflecting surfaces used beingstrictly parallel, it will be understood that focussing can only beeffected for the plane of infinity of the object photographed, and it isconsequently necessary to add to the device, in front of the lens. alarge aperture system of variable focal length which enables any otherplane of the object to be sharply focussed by throwing such plane backto infinity by collimation.

Apart from the very considerable complication implied in the use of acollimating system for this purpose, which has to have a wide apertureand be perfectly corrected, it will be understood that the light yieldof thev assembly is also seriously affected by the number of glasses ofwhich this collimating system is composed.

The present invention has for its object to provide a combineddispersing and blending7 device for the beams of light, of high luminousefficiency and capable of allowing the camera to be sharply A focussedon any plane of the object photographed. It is 'proposed in particularto provide certain forms of construction especially adapted to the casesl. The case in which focussing adjustment has to take place by the usualvariation of the extent to which the objective is moved away from therecording surface, while at the same time, in accordance with theinvention, this result is brought about 'by deformation of the devicefor blending and dividing up the beams without the attachment, infrontoi' the objective, of any system for collimatlng the plane to which thecamera isv focussed.

2. 'I'he case in which it is desired to provide a diaphragm in the planeof the entry face of the blending and dispersing device.

3. The case in which the three colour filter is of circular shape oralternatively of the known shape of a curvilinear lozenge. in order toobtain the best light yield from the objective.

The invention which employs the known expedient of totally or partiallyreflecting surfaces forming an angle oi between them presents thefollowing novel characteristics:

(1) 'I'he division of each of the three coloured bands of the filterinto two segments of equal width, which determines six segments havingin all the same superficial area as the pupil of entry of the cameralens;

(2) The provision of totally or partially refleeting facets projectingnormally t0 the plane of the filter in such a manner that each colouredband may be completely covered bythe projection of merely two facetswhich baille each other either between two superposed tiers or in thesame and single tier;

(3) Such distribution of the beams passing through each segment thatthey emerge either through two, or at the most through three of the sixsegments of the pupil of entry of the v camera lens;

(4) Paths of beams, which, by virtue of this division and the baillearrangement, Vare as short and symmetrical as possible, while the deviceitself is as small as possible in depth, so that, with a minimum ofreflections as set forth above under (3) maximum light yield is secured;

(5) Avoiding the provision in front of the device, of a system forcollimatlng the focussing plane (a system which is generally inseparablefrom light beam blending devices equipped with totally or partiallyreflecting facets), and consequently enabling the handling of the deviceto be simplified while at the same time achieving the nove1 improvementin light yield by subdividing the dispersing and blending device into aplurality of relatively articulated bodies.

Preferred embodiments of the invention are shown, by way of exampleonly, in the accompanying drawing, in which:

Fig. 1 shows, in diagrammatic section, an embodiment of the combinedblending and dispersing device according to the invention.

Fig. 2 shows the entry pupil of the camera lens.

Fig. 3 shows an arrangement constituting a deformable dispersing andblending device.

Figs. 4 and 5 show a simplified modication of the device illustrated inFig. 3.

In Fig. 1, there is represented in section a blending-dispensing devicein accordance with the invention, in which the distribution of the beamsis in a high degree symmetrical. The totally reiiecting facing elementsare shown in full lines and the partially reflecting in broken or dottedlines. For example, the facing elements M3 and M4 may be 66% reflectingand the facing elements M'z and M'e merely 50% reilecting. It will beseen that in this case the ilux falling on the segment I of the face ABof the device, at incidence, emerges in equal parts through the segmentsl and 2 of the face EF on emergence; and that, in a symmetrical manner,the flux incident on AB at 6 emerges at face EF through 6 and 5.

It will also be seen that the flux incident on M2 is divided up betweenthe segments 4, and 6 on emergence, and that, in a symmetrical manner,that incident on M5 is divided up between the segments 3, 2 and i.Finally, it will be seen that the ilux incident on M3 is divided, atemergence, between the segments I, 2, 3, just as that incident on M4 isdivided between the segments 6, 5, 4. It will also be observed that ahighly symmetrical distribution is obtained by masking out thesemi-reflecting i'acing elements Mz and M'e.

In this symmetrical distribution of the beams. given by way of example,the differences of path are slight and negligible, owing to the smalltotal thickness of the two superposed stages (amounting to half thatobtained without the baffling arrangement of the facing elements andwithout dividing the surface of incidence into six segments) and alsoowing to the principle according to which a beam divided at incidencedoes not traverse all the segments of the face at which it emerges butonly. two, or at the most threeof these six segments.

It should be noted that the faces of incidence and emergence of thedevice shown in Fig. l may be interchanged without any alteration in theprinciple of operation of the device.

In Fig. 2 is indicated in outline a iilter having the contour of acurvilinear lozenge, known for giving the diaphragm corresponding to themaximum useful aperture of a camera lens. In order to ensure the mostcorrect use possible o! the pupil of entry furnished by this diaphragm,in combination with the combined blending and dispersing deviceaccording to the invention, the diameterof this diaphragm, measuredperpendicularly to the direction of the coloured bands, is reduced to avalue d which is less by about M3 than the diameter T, by eliminatingthe corners N.

In this way, and at the cost of an insignificant sacrifice of luminosityof this diaphragm, the disparities between the mean values of therespective heights of thesegments l, 2, and 3 (and correspondingly of I,l and L6) is diminished, while at the same time a substantialimprovement is effected in the eilciency of this lter when used with acombined blending and dispersing device according to the invention, ofthe type shown by way of example in Fig. 1.

It will readily be understood, for example, that the iiuxes incident onthe segments 3 and I of the face AB would be reduced to a considerableextent, with reference to the fraction. emerging therefrom through thesegments i and 6, if this precaution were not taken.

It is assumed that the lozenge shape with truncated corners delimits,without varying, the emergent face EF oi' the device, whereas there maybe utilized a circular diaphragm of variable diameter, an iris diaphragmfor example, in the plane of the incident face AB, centered on the axisof the camera lens. For this purpose it is necessary that the ratiobetween the iiux emerging through the central band, on the one hand, andthat emerging through one of the side bands oi' the lozenge-shapediilter, on the other hand, remain substantially constant when thediameter of the diaphragm varies.

It is known that when a three colour filter comprises three bands of thesame breadth occupying the pupil of entry of maximum useful aperture, itis necessary to obscure the central coloured band of this iilterrelatively to the neighbouring bands, on account oi.' its greaterheight.

This greater degree of opacity could not however` in practice beimparted to it in the present device without effecting variation of theratio between the fluxes discussed above when the diameter of an irisdiaphragm placed in the plane of incidence AB oi.' the device is causedto vary.

Calculation shows indeed that the ratio between `the flux emerging fromthe central band of the filter and that emerging from one of the sidebands varies with the aperture of the iris diaphragm disposed in frontof the blending and dispersing device, in the vicinity of its surface ofincidence AIB, in a different manner according to the degree oireflection taken for the partially reiiecting facets of the device.There are consequently represented in this Fig. 2 what might quitesimply be masks K associated with the central band, providing thescreening effect referred to above, as desirable, in the event i'orexample of the facets M3 and M4 being semireflecting and the :lacets M2and M's dispensed with. in order that, when the filter is of the kindwhich is balanced at full aperture, this equilibrium is automaticallymaintained whatever be the diameter of the diaphragm G susceptible ofvariation between full aperture and d/n, n being any number which maypossibly be greater or smaller than the number 3.

In Fig. 3 the body Cn of the central facing elements M3 and M4 is fixedand assumed to be integral with the filter b, v, r and with theobjective the central portion of which is indicated at O. It will beunderstood that symmetrical rotational movements of the two lateralbodies C1 and C2 pivoted at O1 and O2, provided these rotationalmovements equal the same appropriate fraction of the parallax of anobject point in the focussing plane, will produce. between the beams ofthe reflected flux and the beams pertaining to the direct flux, thedesired deviations for the purpose of ensuring that these various fluxescombine exactly to form the same image of the assasec said point. Inthis figure there is no longer any direct flux except for that whichpasses without reflection through the central fixed body Co. 'I'he beamsincident on the faces M1 and Me are the only ones which undergo an evennumber of reflections in one and the same body. But it will be seen,with reference to Fig, 3, that, since the faces M'a and M's of thearrangement shown in Fig. 1 are omitted, the beams incident on thesegments I and 6 of the plane AB emerge at d/6 from their respectivepoints of incidence through the segments 2 and 5 of the plane EF'. Inorder to ensure, on emergence from the device, the propagation of thesebeams which coact with the beams of the direct flux in the formation ofthe samev image of the object focussing plane, it is necessary that oneof the faces at which these beams are reflected an even number of timesin a lateral body of the device, be turned in the appropriate sense,relatively to the other neighbouring face or faces, through an anglewhich is half that required for facing elements spaced apart by d/3 andpertaining to two adjacent pivoted bodies. This rotation is permitted,in the case of the embodiment shown in Fig. 3 for example, bysupplementarily pivoting the I facets M1 and M1, at U1 and U2, on thelevers L1 and L2, respectively, pertaining to the mounting for the twoarticulated slide bodies C1 and Ca. This rotary adjustment iscontrolled, when these levers are moved by extension of the lens O inthe course of focussing, with consequent adjustment of the lensrelatively to the ilxed point of articulation on the camera, for exampleby the abutment of fingers such as S1 and S2 against blocks P1 and P2secured for example to the lens mounting; these fingers, which aresecured to the articulated mountings of the facets M1 and M7, are ofsuitable profile.

It will be understood that if the facets Mz and M's are held in positionon the device shown in Fig. 3, in the manner indicated in Fig. 1, itwould also be necessary to make these facets articulated like the facetsM1 and M7 on the mountingsLi and L11 of the side bodies C1 and C2. It isin fact necessary, on the one hand, that the fractions of each of thebeams incident on the segments l and t of the surface AB, which are alsoreflected by each of the facets M2 and M, shall not undergo anydeflection on emergence from the device, because these fractions,emerging through segments of the face EF denoted by the same indices land 6 asthose of the entry face, are comprised in the direct flux. Onthe other hand, it is also necessary, and at the same time, that thefractions of beams striking these facets Mfz and Me and coming byreflection on the facets M3 and M4, and which emerge through thesegments 2 and 5 of the face EF, be deflected through the anglecorresponding to the deviation d/6 which exists only between the pointsof incidence and emergence of the rays of these fractions of beams,Finally, this articulation of the facets M'z and M's has no eect uponthe fractions of these same beams which traverse them and emerge throughthe segments i and 6 of the face EF, nor on those which emerge throughthe segments 2 a'nd 5 of the face EF and derived from beams incident onthe segments l and ii of the face AB. Thus, these various fractions onlyundergo, respectively, as has been seen above to be necessary,deviations imposed by rotation of the facets M1 and M'z regulatedvon theone hand for the spreading to the extent of d/6 extant between thepoints of incidence and emergence of the rst of these fractions ofbeams, and by rotation of the bodies C1 and Ca regulated on the otherhand for the spreading to the extent of d/3 established between thepoints of incidence and emergence of the second of these fractions ofbeams.

It will also be understood, as explained in connection with Fig. 1,that, mutatis mutandis, the

Aface of incidence and emergence AB and EF respectively of the deviceshown in the Fig, 3 may be interchanged without in any way altering thedesired result.

It is self-evident that, as stated in the parent patent, the cylindricalseparation surfaces of the prismatic elements presenting totally orpartially reflecting faces, are bathed by a relatively nonvolatileliquid having a coeillcient of refraction closely approximating to thatof the substance of which the device is composed, or alternatively, thataccording to themode of construction indicated by Brewster in his U. S.Patent No. 1,277,040, 1918, and for the purposeof substitutingmetallized mirrors which are totally or partially reflecting, for theprismatic elements of a beam dividing or dispersing device, theseparation surfaces of articulated bodies may also be immersed togetherwith the whole of the device, in a tank containing liquid of suchcomposition that its refractive index renders absolutely invisible theglass of the mirrors of which only the metallized surface reflects. Forthis purpose it is known to employ aqueous solutions of iodo-mercuriateof barium, potassium, or sodium, the refractive index of which mayattain the figure 1.7.

Figs. 4 and 5 represent, in section and in plan view respectively, adevice in which the six segments of the diaphragm (assumed to becircular) delimiting the illter, are divided into two groups of threeseparated by a diameter lying transversally of the bands b, v, r of thisthree colour filter, and in which the odd and even facets cross eachother at 90. These facets occupy for example the entire thickness e ofthe device, which is equal to the thickness of the two superposed tiersof the preceding devices, and, for example, the facets M2 and M5 are 66%reflecting, the facets M3 and M4 50% reflecting, and the facets M1 andMe 100% reflecting. All are symmetrical again in respect of the paths ofrays in the two groups of facets, but a substantial fraction of theincident beams is lost by the totally reflecting facets.

The efllciency of the device and the distribution of the beams betweenthe central and side segments may be very considerably improved bymaking them all of the same maximum height H/2, which increases theparts reflected by the side facets and destined to traverse the segmentscovered overrv by the other facets. v

In these latter combinations, it is sufficient for the facets to bedivided uplbetween three bodies C0, C1, Cz, in order to ensure, byarticulation about the axes O1 O1, Oz O'z, correct focussing thecoloured fluxes on emergence, Ain disposing masks such as K ofappropriate pre-determined.

shape, on the central coloured band.

` The invention also extends, and notably so, to all combinations of theaforesaid embodiments, in which there will invariably be observed inpart or in their totality the characteristics of the invention.

I claim:

l. In a photographic system for making exposures in three colours onlenticular films, apparatus comprising an optical device having a set ofentrance zones and a set of exit zones for light, the number of each setof zones being six. an objective, a three-colour filter between saidoptical device and said objective, `said. optical device including meansfor blending and dispersing beams of light rays mounted in front of saidobjective and comprising plane facets disposed in a single tier havingtwo portions each affected to the extentfof one half by the colournlter, according to a diametrical division at right angles to the linesof separation between its coloured zones, the inclination of the facetsin one of the two portions of theblending and dis- -persing means beingdifferent from the inclination of the facets in the other of the saidportions, the opposite faces of each facet being parallel and saidfacets being disposed in such a manner that each of the beams reflectedonce by one of said facets and reflected a second time by others of thesaid facets, traverses at .least one sixth and at the most one half ofthe whole of the coloured zones of the said filter, said reilectingfacets being parallel in each of said portions and at right angles asbetween portions.

2. In a photographic system for making exposures in three colours onlenticular films, apparatus comprising an optical device having a set ofentrance zones and a set of exit zones for light, the number of each setof zones being six, an objective, a three-colour filter between saidoptical device and said objective, said optical device including meansfor blending and dispersing beams of light rays mounted in front of saidobjective and comprising plane facets disposed in a single tier havingtwo portions each affected to the extent of one half by the colourfilter, according to a diametrical division at right angles to the linesof separation between its coloured zones, the inclination of the facetsin one o! the two portions of the blending and dispersing means beingdifferent from the inclination of the facets in the other of the saidportions, the opposite faces of each facet being par-r allel and saidfacets being disposed in such a manner that each of the beams reflectedonce by one of said facets and reflected a second time by others of thesaid facets, traverses at least one sixth and at the most one half ofthe whole of the coloured zones of the said filter, the said blendingand dispersing means comprising a central body fixed relatively to theobjective and covering the central band of the said three-colour filter,while the side bodies covering the side bands of the filter arearticulated about axes pertaining to the objective and are actuated bymovement of the objective in focussing the camera on the object to bephotographed, said refleeting facets being parallel in each of saidportions and at right angles as between portions.

3. In a photographic system for making exposures in three colours onlenticular films, apparatus comprising an optical device having a set ofentrance zones and a set of exit zones for light. the number of each setoi zones being six. an objective, a three-colour illter between saidoptical device and said objective, said optical device including meansfor blending and dispersing beams of light rays mounted in front of saidobjective and comprising plane facets disposed in two superposed tiersand at right angles as between tiers, having the same inclination ineach tier, those of one tier being arranged to displacement of theobjective in the course of its movement for bringing the object to bephotographed into focus, facets of each of the said side bodies beingseparately articulated on the said bodies and adapted to carry outrotational movements different from the movements of said bodies in thecourse of the focussing operation, some of said facetsbeing totallyreflecting and others being partially redecting and partiallytransmitting, said facets being disposed in such a manner that each ofthe beams reflected once by one of said facets and reflected a secondtime by others of the said facets, traverses at least one sixth and atthe most one half of the whole of the coloured zones of the said filter.

4. In a photographic system for making exposures in three colours onlenticular films, apparatus comprising an optical device having a set ofentrance zones and a set of exit zones for light, the number oi each setof zones being six. an objective, a three-colour illter between saidoptical device and said objective. said optical device including meansior blending and dispersing beams of light rays mounted in front of saidobjective and comprising plane reflecting facets arranged in two rowsoi' opposite inclination, the opposite faces of each facet beingparallel, the adjacent faces of all 'of said facets being reflecting andsome ci 'them being completely reflecting and others being partiallyreflecting and partially transmitting, said facets being disposed insuch a manner that each of them only covers half a coloured zone of 'thesaid filter and that each of the beams reflected once by one of saidfacets and reflected a second time by others of the said facets,traverses at least one sixth and at the most one half ofthe Whole of thecoloured zones of the said filter, said blending and dispersing meansbeing associated with a variable aperture iris diaphragm and with masksso associated with said filter as to mask the central band thereof andof such shape that variations in the aperture of said diaphragm do notmodify appreciably the balance of the colours. said reflecting facetsbeing parallel in each row and at right angles as between rows.

5. A light blending device for use in a photographic system for makingexposures on lenticular films, said device comprising a transparent bodyhaving a set of six light entrance zones provided with an entrance faceand a set of six light exit zones provided with an exit face which isparallel to said entrance face. facets provided in said body in tworows. one row of facets being adjacent the entrance face and the secondrow of facets being adjacent the exit face, the facets in the two rowsbeing oppositely inclined relatiw to each other, the faces ot the'facets in one row being parallel as respect to each other and at 'rightangles as respect to the facets inA the opposite row, the adjacentfacesY of all of said facets being reflecting and some of the adjacentfaces being completely reflecting while others are partially reectingand partially transmitting, each facet being positioned to extend acrossa separate zone, the facets adjacent said entrance face being locatedacross the 'rst, second. fourth and sixth zones counting from one end ofthe device and the facets adjacent said exit tace

